1. Field of the Invention
The invention concerns an electrostatic device for spraying an electrically conductive liquid coating product such as a water-based paint. It is more particularly concerned with a compact and lightweight unit including a storage tank for a product of this kind which is usually at a high voltage during spraying, the unit being adapted to prevent the establishment of any tracking current between a part at the high voltage and any other part which is designed to be at a different potential, typically ground potential.
The invention is more particularly, but not exclusively, concerned with a unit incorporating an intermediate storage tank of this kind and at least one electrostatic sprayer which is sufficiently compact and light in weight to be carried by a multi-axis robot whose various articulated segments are grounded.
2. Description of the Prior Art
The patent U.S. Pat. No. 4 785 760 describes an electrostatic system for spraying a conductive coating product which is noteworthy in that the quantity of product required to paint an object is stored in a storage tank carried by a multi-axis robot. The latter carries the electrostatic sprayer in the immediate vicinity of the storage tank. It may advantageously also carry at least the high-voltage part of the electrical power supply. The high-voltage output of the power supply is connected to the sprayer with the result that all of the conductive coating product in the storage tank is at the high voltage. A system of this kind has two major advantages. It eliminates long hoses between the coating product distribution circuit and the sprayer carried by the robot, which saves significant quantities of coating product each time the product is changed, i.e. each time the color is changed, and it makes it a simple matter to provide the necessary galvanic insulation between the storage tank and the supply circuit (which is grounded) during spraying when the coating product is a conductive product applied electrostatically.
The invention concerns a compact and lightweight insulated intermediate storage tank of this kind adapted to contain a conductive coating product at a high voltage.
The device of the invention is noteworthy by virtue of the set of arrangements adopted to prevent the formation of leakage currents resulting from so-called "tracking" phenomena along surfaces which are in theory insulated between a member at the high voltage and any member at a different potential, in particular ground potential.